Marine propeller

ABSTRACT

A marine propeller includes a hub defining an axial direction of the propeller, a plurality of adjustable propeller blades disposed around the hub, and a blade setting adjusting arrangement. Each blade includes a blade-part and a root-part, the root-part being mounted in the hub and being turnable about an axis that defines an angle with the axial direction of the propeller.

FIELD OF INVENTION

The present invention relates to a marine propeller. The adjustableblades of propellers according to the present invention enable thepropeller to be adapted to different running conditions and differenttypes of engines or motors. One advantage with such propellers is thatthey cover a wider area of use than fixed blade propellers. This enablespropeller manufacturers and suppliers to satisfy the requirements ofdifferent users with a relatively limited number of types of propellerin the general assortment.

BACKGROUND OF THE INVENTION

Adjustable blade propellers have long been known. These propellers canbe divided into two main types, one type with which each blade can beadjusted individually, and another type with which all blades areadjusted commonly in one single movement. One advantage with the lattertype of propeller is that it eliminates the need to bring the individualsetting of a blade into agreement with the settings of the remainingblades, which can be difficult to achieve and which may result indifferences in blade settings.

The inventive propeller lies within this latter type of propeller, i.e.a propeller with which the propeller blades can be adjusted in unison.

Adjustable blade propellers of this kind are described and illustratedin U.S. Pat. Nos. 813,074, 2,574,951, 5,232,345, 2,953,208, 3,403,735,3,308,889, for instance. A common feature of the propeller constructionsdescribed in these publications is that common or unison adjustment ofthe blades is made to a completely optional setting within the limitsgiven, i.e. the blades can be adjusted to different settings smoothlyand continuously. The blades are locked in their new settings,subsequent to this adjustment. This procedure has several drawbacks.Firstly, it is necessary to be able to read or determine the bladesetting, so as to establish whether or not the blade has been adjustedto the angle intended. There is also the risk of deviation between theblade setting intended and the blade setting achieved. Furthermore, itis necessary to rely upon force-bound locking of the blades whenpracticing this continuous blade adjustment principle. This force-boundlocking of the blades can result in a change in the blade setting, ormay require the application of locking forces of such great magnitude asto cause dismantling and fitting operations in respect of the adjustmentmore difficult to achieve and induce higher tensions in the material.There is also the risk of a heavily tightened locking device becomingloose in the passage of time, due to vibration and other forces, so asto disturb the blade settings. As a result, a number of the earlierconstructions have become highly complicated.

EP 0 300 252 teaches a blade adjuster with which the blades can beadjusted to distinct settings in unison. The arrangement is, however,relatively complicated and involves the conversion of a torsionaladjustment movement to an axial adjustment movement of a rod thatextends to each propeller blade, through the medium of nuts andspindles. The axial movement of the rod is then converted to rotationalmovement of respective blades through the medium of a pin carried by therod and co-acting with a guide groove or channel in the blade root.

SUMMARY OF THE INVENTION

Against this background, it is an object of the invention to provide apropeller of the kind concerned with which the aforesaid problemsassociated with known techniques in this field have been avoided. Morespecifically, it is an object of the invention to provide a propeller ofsimple construction with which the blades can be adjusted tounequivocally defined and positively retained settings.

This object has been achieved in accordance with the invention.

Because the common adjustment movement is performed through the mediumof relative movement between two elements, the adjuster ring and thehub, which can be shape-locked together in predetermined distinctpositions, the blades can be adjusted to defined positions such as toeliminate the risk of accuracy deficiency and such as to obviate theneed for measuring a precise position of adjustment or setting. All thatis required to show to which of the predetermined positions theadjustment relates is a simple indication index. The shape-bound lockingfacility also ensures that the blade setting will not be disturbed andaffected by vibrations and running disturbances. The inventive propelleris also of simple construction and therewith relatively inexpensive inmanufacture.

According to one preferred embodiment of the invention, the means bywhich the adjustment adjuster ring and the hub are locked relative toone another in their circumferential direction are disposed on themutually facing surfaces of said adjuster ring and said hub.

The locking elements suitably have the form of axially extending teethwith intermediate grooves or channels on each of the two surfaces.

The grooves and teeth have a complementary shape, so as to engage withone another in locking the adjuster ring and the hub together. One ofsaid surfaces will include a plurality of teeth and the other at leastone tooth, preferably several teeth. The teeth and the grooves ensurethat the shape-bound locking effect is achieved and also define theblade settings.

According to another preferred embodiment, the movement transmissionelement that transmits rotation of the setting adjuster ring to thepropeller blades is comprised of a plurality of arms, each of which isconnected at one end to the root of a blade and the other end of whichprojects into a respective recess provided in the blade setting adjusterring. This provides simple and reliable transmission of rotation of theadjuster ring to rotation of the propeller blades.

As a result of this simple construction of the blade adjustingmechanism, space can be provided for accommodating exhaust passages inthe hub. A preferred embodiment of the invention thus includes such anarrangement of exhaust passages. This facility provided by saidconstruction is particularly beneficial in view of the fact that thepropeller is intended for use with several different types of drivemotors.

According to one particularly beneficial embodiment of an inventivepropeller, the blades are flexible so that their propelling behaviourwill be influenced by operating or running conditions, which is ofparticular importance when the propeller blades can be adjusted indistinct steps. A preferred embodiment of the invention also relates tothis facility.

According to another preferred embodiment, each blade has a weakenedpart that forms a fracture location. This prevents the hub from beingdamaged in the event of the propeller blades striking against a stone orsome other object. This is of particular importance in respect of aninventive propeller, since a hub that is constructed for stepwiseadjustment of the blade settings is more sensitive to external forcesthan a hub to which the blades are fixedly connected.

The features and advantages of the present invention are well understoodby reading the following detailed description in conjunction with thedrawings in which like numerals indicate similar elements and in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of an inventive propeller.

FIG. 2 is a side view of a propeller blade of an inventive propeller.

FIG. 3 is a sectional view taken on the line III—III in FIG. 2.

FIG. 4 is a view seen radially inwards of the blade in FIG. 2.

FIG. 5 illustrates the hub of an inventive propeller partly in side viewand partly in axial section.

FIG. 6 is a sectional view taken on the line VI—VI in FIG. 5.

FIG. 7 is a sectional view taken on the line VII—VII in FIG. 5.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 is an exploded view of an inventive propeller assembly whichcomprises a hub that includes a forward hub-half 1 and a rearwardhub-half 2, a unit 3 for connection to the gear box of a drive motor, anadjustment adjuster ring 4, and four propeller blades 5, of which onlytwo are shown in the Figure. Each of the two hub-halves 1, 2 is providedwith four semi-circular recesses 6 a, 6 b which are located centrally ofeach other and which when assembled form circular bearings 6 forrespective blades 5 y. Each blade 5 has a circular base-part orroot-part 7 by means of which it is rotatably mounted in one of thebearings 6. The two hub-halves 1, 2 are held together by four bolts (notshown) drawn through holes 8, 9 in the front and rear hub-halvesrespectively. The hub-parts include axially through-passing passages 10,11 through which motor exhaust gases can pass. The propeller is drivenby a shaft (not shown) extending from a motor, and the shaft isdrivingly connected to the hub bore 12 in the rear hub-half 2, forinstance by means of a spline coupling.

The root-part 7 of each blade includes a circumferentially extendingprojection 13 which projects out radially in relation to the rotationalaxis of the blade and which coacts with a corresponding groove orchannel 14 in the hub-halves for mounting the blades to the hub andsecures the blades in the radial direction of the propeller. A bladeadjusting arm 15 is attached to the periphery of each root-part andextends generally radially relative to the rotational axis of the blade,i.e. extends generally in the direction of the propeller axis. The bladesetting is adjusted by applying torque to the arm 15. When fitted, thearm 15 extends inwardly of the outer surface of the rear hub-half 2 andback towards the setting adjuster ring 4. Each arm 15 has a flaredend-part 16 which, when the arm is fitted, is received in a recess 17 onthe inner surface of the adjuster ring.

In operation, the adjuster ring 4 is fitted to the rear hub-half 2,wherewith a front annular end-surface 18 abuts a rear end-surface 19(obscured in FIG. 1) of the rear hub-half 2. In this assembled statesthe adjuster ring 4 is fastened to the hub-half 2 by means ofappropriate fasteners (not shown) and is secured against rotation byaxially extending teeth 20 and intermediate grooves 21 on theend-surface 18 of the adjuster ring, said teeth and grooves co-actingwith correspondingly shaped teeth and grooves 23 (obstructed in FIG. 1)on the end-surface 19 of the rear hub-part 2.

The adjuster ring 4 can be loosened from the rear hub-half 2 so as to bemovable axially in relation thereto, and can be displaced slightlytherefrom to a second position in which the teeth and grooves 20, 21,22, 23 no longer co-act with one another. The adjuster ring 4 can berotated relative to the rear hub-half 2 in this position. By rotatingthe adjuster ring 4 slightly and then re-fastening it to the rearhub-half 2, the teeth and the grooves 20, 21, 22, 23 will lock theadjuster ring in the new position. Rotation of the adjuster ringinvolves moving the adjuster ring axially through only a short distancesuch as to ensure that the teeth and the grooves are out of mutualengagement. However, the end-part 16 of respective blade settingadjusting arms 15 still protrude into the recesses 17 on the adjusterring 4 in this position.

Thus, rotation of the adjuster ring 4 causes each arm 15 to rotate theroot-part 7 of respective blades to a setting that depends on the anglethrough which the adjuster ring is rotated.

The positions to which the adjuster ring of the illustrated constructioncan be rotated are restricted to a number of distinct positionsdetermined by the pitch of the teeth 20, 22. The blade settings can thusbe adjusted incrementally and the number of setting positions isdependent on the number of teeth on the adjuster ring or on the rearhub-half. The adjuster ring 4 and the rear hub-half 2 need not have thesame number of teeth. The number of rotational positions is determinedby the unit that has the most teeth.

In principle, it is conceivably sufficient to provide the describedlocking device with teeth on only one peripheral part of the end-surfaceof the adjuster ring and the rear hub-half respectively. However, it maybe convenient to provide corresponding pairs of engaging teeth atseveral places on these surfaces, as shown at 24 and 15 in the Figure.This arrangement provides a more positive locking effect.

In order to show visually the distinct rotational positions in which therear hub-half 2 and the adjuster ring 4 are located, there is provided ascale 27 that includes a number of index marks on the outer surface ofthe rear hub-part 2, adjacent its end-surface 19. A setting marking 26is provided at a corresponding position on the outer surface of theadjuster ring 4. The position of the setting marking 26 on the scale 27therewith shows the rotational position of the blades.

Since all blades are provided with an adjusting arm 15 that co-acts witha respective recess 17 on the adjuster ring 4, the blades 5 will berotated in unison as the adjuster ring 4 rotates.

FIG. 2 illustrates in more detail the annular projections 13 andassociated blade adjusting arms 15 adapted for mounting and radiallysecuring the root-part 7 of each blade 5.

FIG. 3 is a sectional view taken on the line III—III in FIG. 2 and showsthat the root-part 7 of the blade is hollow and includes an annular parton which the projections 13 are provided and a dome-shaped part 28connected integrally with the actual blade 5. The inner surface of thedome-shaped part 28 has a circumferentially extending groove 29 whichweakens the blade at its root and therewith functions as a fracturelocation. In the event of the blade 5 striking an obstacle, such as astone, the blade will fracture at the groove 29 before the force reachesthe hub and damages the same. This arrangement limits propeller damageto the blade whilst protecting the hub. It will be borne in mind thatthe hub of a propeller assembly that includes a blade setting adjustingarrangement of this kind is more expensive and less robust than the hubof a conventional propeller with fixed blades.

The propeller blades 5 are preferably made of a flexible material, forinstance a plastic composite. When the blade 5 has a rearwardly sweptprofile, the outer part of the rear edge 30 of the blade will be urgedforwards through an angle corresponding to the angle α and reach aforwardly displaced position indicated by the broken line in FIG. 4,therewith reducing the pitch. This takes place when the blade issubjected to a high load, for instance in response to acceleration. Thegreater the load, the greater the reduction in pitch, resulting ineasier propulsion. There is thus obtained in this way some sort of“automatic gear function” which automatically reduces the pitch when thepropeller is subjected to heavy loads, due to the flexibility of thematerial.

FIG. 5 is a cross-sectional view illustrating attachment of the blade 5in the circular opening 6 formed between the two hub-parts 1, 2. Theperipheral projections 13 on the blade root 7 co-act with grooves orchannels 14 on the hub-halves, so as to secure and rotatably mount theblade in the hub. The end-part 16 of respective blade setting adjustingarms 15 extend into the recess 17 so as to be entrained by the adjusterring 4 as it rotates and therewith rotate the blade 5. The adjuster ring4 is shown in a locked position with its end-surface in abutment withthe rear end-surface of the rear hub-half and with the mutuallyco-acting teeth and grooves (not visible in this Figure) on saidsurfaces in mutual locking engagement. Also shown in the Figure are fourbolts 31 which hold the hub together. When adjusting the setting of theblades, the bolts 31 are first loosened sufficiently to enable theadjuster ring 4 to be moved axially through a distance required to movethe teeth and the grooves out of engagement with one another andtherewith enable the adjuster ring to be turned. Subsequent to turningthe adjuster ring to a new position, the bolts are tightened in thisposition and the blade setting marking 26 is moved to another positionopposite some other marking on the scale 27. The markings 26 and 27 mayhave the form of a painted line or a scored line.

FIGS. 6 and 7 are sectional views taken respectively along the linesVI—VI and VII—VII in FIG. 5 and serve to further illustrate the mutualrelationship of elements significant to blade setting adjustment. Theabove description made with reference to FIGS. 1 and 5 is believed tomake FIGS. 6 and 7 self-explanatory.

What is claimed is:
 1. A marine propeller comprising: a hub defining anaxial direction of the propeller; a plurality of adjustable propellerblades disposed around the hub; a blade setting adjusting arrangement;each blade including a blade-part and a root-part, the root-part beingmounted in the hub and being turnable about an axis that defines anangle with the axial direction of the propeller; the blade settingadjusting arrangement being arranged to turn all blades in unison andincluding a blade setting adjusting ring including first locking meansthat coact with complementary second locking means provided on the hub,the adjuster ring being axially movable between a first axial positionin which the first and the second locking means are in mutual lockingengagement and a second axial position in which the first and the secondlocking means are out of engagement with one another and in which theadjuster ring is turnable relative to the hub, the first locking meansand the second locking means permitting a plurality of distinctrotational positions of the adjuster ring relative to the hub, the bladesetting adjuster ring being connected to each of the plurality ofpropeller blades by a movement transmission means for adjusting therotational position of each propeller blade of the plurality ofpropeller blades incrementally in relation to a selected rotationalposition of the adjuster ring, the movement transmission means includinga plurality of substantially axially extending adjusting arms, whereinone end of each arm of the plurality of arms is non-rotatably connectedto a root-part of a propeller blade of the plurality of propeller bladesand the other end of each arm of the plurality of arms is connected tothe adjuster ring, and wherein the other end of each arm is adapted toaccompany the adjuster ring as it is turned, wherein the adjuster ringhas a first surface which faces towards the hub, and the hub has asecond surface which faces towards the adjuster ring, and wherein thefirst locking means and the second locking means are arranged on thefirst and second surfaces, respectively, and wherein one of the firstlocking means and the second locking means includes a plurality ofaxially extending teeth which are disposed adjacent each other in thecircumferential direction and mutually separated by intermediate groovesor channels, and wherein the other of the first and said second lockingmeans includes at least one axially extending tooth that has a shapecomplementary to the grooves or channels.
 2. A propeller according toclaim 1, wherein the rotational axis of each root-part extendssubstantially perpendicular to the axial direction of the propeller, andwherein all of the rotational axes of all of the roots of all of theplurality of propeller blades are located in a common radial plane.
 3. Apropeller according to claim 2, wherein the adjuster ring includes anumber of arm-receiving recesses, and wherein, for each arm of theplurality of arms, the other end extends into one of the recesses.
 4. Apropeller according to claim 2, wherein the hub and the adjuster ringinclude indicating means which function to indicate to which of thedistinct positions the adjuster ring and the hub are turned in relationto one another.
 5. A propeller according to claim 1, wherein theadjuster ring includes a number of arm-receiving recesses, and wherein,for each arm of the plurality of arms, the other end extends into one ofthe recesses.
 6. A propeller according to claim 5, wherein the hub andthe adjuster ring include indicating means which function to indicate towhich of the distinct positions the adjuster ring and the hub are turnedin relation to one another.
 7. A propeller according to claim 1, whereinthe hub includes axially extending passages through which exhaust gasesgenerated by a motor driving the propeller can pass.
 8. A propelleraccording to claim 1, wherein each blade is made of a flexible materialof sufficient flexibility to enable the shape of the blade to be changedby forces applied on the blade during operation in water.
 9. A propelleraccording to claim 1, wherein each blade includes a weakened part thatforms a fracture location.
 10. A propeller according to claim 1, whereinthe hub and the adjuster ring include indicating means which function toindicate to which of the distinct positions the adjuster ring and thehub are turned in relation to one another.